Are young injection drug users ready and willing to participate in preventive HCV vaccine trials?

Reducing Sample Size While Improving Equity in Vaccine Clinical Trials: A Machine Learning-Based Recruitment Methodology with Application to Improving Trials of Hepatitis C Virus Vaccines in People Who Inject Drugs

Despite the availability of direct-acting antivirals that cure individuals infected with the hepatitis C virus (HCV), developing a vaccine is critically needed in achieving HCV elimination. HCV vaccine trials have been performed in populations with high incidence of new HCV infection such as people who inject drugs (PWID). Developing strategies of optimal recruitment of PWID for HCV vaccine trials could reduce sample size, follow-up costs and disparities in enrollment. We investigate trial recruitment informed by machine learning and evaluate a strategy for HCV vaccine trials termed PREDICTEE-Predictive Recruitment and Enrichment method balancing Demographics and Incidence for Clinical Trial Equity and Efficiency. PREDICTEE utilizes a survival analysis model applied to trial candidates, considering their demographic and injection characteristics to predict the candidate's probability of HCV infection during the trial. The decision to recruit considers both the candidate's predicted incidence and demographic characteristics such as age, sex, and race. We evaluated PREDICTEE using in silico methods, in which we first generated a synthetic candidate pool and their respective HCV infection events using HepCEP, a validated agent-based simulation model of HCV transmission among PWID in metropolitan Chicago. We then compared PREDICTEE to conventional recruitment of high-risk PWID who share drugs or injection equipment in terms of sample size and recruitment equity, with the latter measured by participation-to-prevalence ratio (PPR) across age, sex, and race. Comparing conventional recruitment to PREDICTEE found a reduction in sample size from 802 (95%: 642-1010) to 278 (95%: 264-294) with PREDICTEE, while also reducing screening requirements by 30%. Simultaneously, PPR increased from 0.475 (95%: 0.356-0.568) to 0.754 (95%: 0.685-0.834). Even when targeting a dissimilar maximally balanced population in which achieving recruitment equity would be more difficult, PREDICTEE is able to reduce sample size from 802 (95%: 642-1010) to 304 (95%: 288-322) while improving PPR to 0.807 (95%: 0.792-0.821). PREDICTEE presents a promising strategy for HCV clinical trial recruitment, achieving sample size reduction while improving recruitment equity.

A cross-sectional survey of potential factors, motivations, and barriers influencing research participation and retention among people who use drugs in the rural USA

BACKGROUND

Despite high morbidity and mortality among people who use drugs (PWUD) in rural America, most research is conducted within urban areas. Our objective was to describe influencing factors, motivations, and barriers to research participation and retention among rural PWUD.

METHODS

We recruited 255 eligible participants from community outreach and community-based, epidemiologic research cohorts from April to July 2019 to participate in a cross-sectional survey. Eligible participants reported opioid or injection drug use to get high within 30 days and resided in high-needs rural counties in Oregon, Kentucky, and Ohio. We aggregated response rankings to identify salient influences, motivations, and barriers. We estimated prevalence ratios to assess for gender, preferred drug use, and geographic differences using log-binomial models.

RESULTS

Most participants were male (55%) and preferred methamphetamine (36%) over heroin (35%). Participants reported confidentiality, amount of financial compensation, and time required as primary influential factors for research participation. Primary motivations for participation include financial compensation, free HIV/HCV testing, and contribution to research. Changed or false participant contact information and transportation are principal barriers to retention. Respondents who prefer methamphetamines over heroin reported being influenced by the purpose and use of their information (PR = 1.12; 95% CI: 1.00, 1.26). Females and Oregonians (versus Appalachians) reported knowing and wanting to help the research team as participation motivation (PR = 1.57; 95% CI: 1.09, 2.26 and PR = 2.12; 95% CI: 1.51, 2.99).

CONCLUSIONS

Beyond financial compensation, researchers should emphasize confidentiality, offer testing and linkage with care, use several contact methods, aid transportation, and accommodate demographic differences to improve research participation and retention among rural PWUD.

Willingness to participate in hepatitis C vaccine trials among socially marginalized people who use drugs

A major complicating factor for hepatitis C virus (HCV) vaccine clinical trial design and implementation is engagement and retention of people who use drugs (PWUD). Informed willingness to participate (WTP) in vaccine trials has emerged as a critical issue to describe, understand, and promote among populations at increased risk of communicable disease incidence. The present study addressed this topic by examining correlates of WTP among 320 socially marginalized PWUD as part of the Edmonton Drug Use and Health Survey (EDUHS). WTP was analyzed in relation to: gender, age, housing stability, ethnicity; self-reported hospital care in the past six months, self-reported injection drug use in the past 6 months, lifetime addiction treatment for alcohol or drugs, severity of drug use problems, and unmet healthcare needs. EDUHS participants reported high rates of current injection drug use (91%), and about two-thirds (67.3%) reported a lifetime HCV positive status. HCV positive respondents were older, had more severe substance use problems, and reported injecting drugs more frequently, compared to HCV negative respondents. Among the subsample of HCV negative respondents, 81% affirmed that they would be willing to enroll in a HCV vaccine prevention trial. Those reporting WTP were more likely to have had a recent hospital admission, to report more total unmet healthcare needs, and greater unmet needs for information, hospital care, and counseling, compared to HCV negative respondents not willing to enroll in a vaccine trial. No association was observed between WTP and other assessed variables. Results suggest that connecting PWUD not infected with HCV to local healthcare resources may be important in motivating vaccine trial participation.

Barriers and motivations to volunteers' participation in preventive vaccine trials: a systematic review

INTRODUCTION

The recruitment of volunteers in preventive vaccine trials (PVT) is a challenge, since vaccine hesitancy and debates on vaccines are combined to usual difficulties of enrollment in clinical trials. Areas covered: Current knowledge of the reasons leading to the volunteers' participation or non-participation in PVT mainly focuses on data from preventive HIV vaccine trials. A systematic PubMed search was conducted using PRISMA guidelines to identify articles or reviews that reported barriers and motivations to participation in PVT regardless of the targeted disease or population. Expert commentary: In view of the barriers and motivations reviewed here, improvements in recruitment could be made through a better explanation of the prevented disease, of the expected individual and collective benefit and of all ethical protective principles associated to the trials. Use of decision aids as well as patient and public involvement may improve given information and may enhance comprehension of participants and their participation in PVT. Further prospective and interventional studies are needed to analyze if these leads may improve acceptation level in PVT.

Factors associated with willingness to participate in a pharmacologic addiction treatment clinical trial among people who use drugs

BACKGROUND AND OBJECTIVES

Although new medications are needed to address the harms of drug addiction, rates of willingness to participate in addiction treatment trials among people who use drugs (PWUD), have not been well characterized.

METHODS

One thousand twenty PWUD enrolled in two community-recruited cohorts in Vancouver, Canada, were asked whether they would be willing to participate in a pharmacologic addiction treatment trial. Logistic regression was used to identify factors independently associated with a willingness to participate.

RESULTS

Among the 1,020 PWUD surveyed between June 1, 2013 and November 30, 2013, 58.3% indicated a willingness to participate. In multivariate analysis, factors independently associated with a willingness to participate in a pharmacologic addiction treatment trial included: daily heroin injection (Adjusted Odds Ratio [AOR] = 1.75; 95% Confidence Interval [CI]: 1.13 - 2.72); daily crack smoking (AOR = 1.81; 95% CI: 1.23 - 2.66); sex work involvement (AOR = 2.22; 95% CI: 1.21 - 4.06); HIV seropositivity (AOR = 1.49; 95% CI: 1.15 - 1.94); and methadone maintenance therapy participation (AOR = 1.77; 95% CI: 1.37-2.30).

DISCUSSION AND CONCLUSIONS

High rates of willingness to participate in a pharmacologic addiction treatment trial were observed in this setting. Importantly, high-risk drug and sexual activities were positively associated with a willingness to participate, which may suggest a desire for new treatment interventions among PWUD engaged in high-risk behavior.

SCIENTIFIC SIGNIFICANCE

These results highlight the viability of studies seeking to enroll representative samples of PWUD engaged in high-risk drug use.

Hepatitis C vaccine clinical trials among people who use drugs: potential for participation and involvement in recruitment

Candidate prophylactic HCV vaccines are approaching phase III clinical trial readiness, yet little is known about the potential for participation among target groups or innovative ways to promote enrollment within 'hard-to-reach' populations. This study describes HCV vaccine trial participation willingness among a high-risk sample of people who use drugs and their willingness to assist researchers by promoting the trial among peers. Willingness to participate in and encourage peers' participation in an HCV vaccine trial was assessed among injection and non-injection drug users enrolled in a cohort study in Kentucky using interviewer-administered questionnaires (n=165 and 415, respectively, with willingness to participate assessed among HCV-seronegative participants only). Generalized linear mixed models were used to determine correlates to being "very likely" to participate or encourage participation in a trial. Most reported being likely to participate or encourage participation in a vaccine trial (63% and 87%, respectively). Men were significantly less likely to report willingness to encourage others' participation, while willingness to encourage was higher among lower income, HCV-seropositive, heroin-using, and methamphetamine-using participants. Unemployment, lesser education, receipt of financial support from more peers, and nonmedical prescription drug use were positively associated with willingness to participate. Differential enrollment in HCV vaccine clinical trials by socioeconomic status may occur, underscoring ethical considerations and need for avoiding coercion. Notably, the data suggest that a peer-driven approach to promoting trial participation among people who use drugs could be feasible in this population and that HCV-seropositive individuals and women could be especially instrumental in these efforts.

Detection of HCV-Specific IFN-γ Responses in HCV Antibody and HCV RNA Negative Injecting Drug Users

BACKGROUND

Detectable HCV-specific cellular immune responses in HCV antibody and RNA negative people who inject drugs (PWID) raise the question of whether some are resistant to HCV infection. Immune responses from people who have been exposed to hepatitis C virus (HCV) and remain anti-HCV negative are of interest for HCV vaccine development; however, limited research addresses this area.

OBJECTIVES

In a cohort of HCV antibody and RNA negative PWID, we assessed whether the presence of HCV-specific IFN-γ responses or genetic associations provide any evidence of protection from HCV infection.

PATIENTS AND METHODS

One hundred and ninety-eight participants were examined longitudinally for clinical, behavioral, social, environmental and genetic characteristics (IFNL3 genotype [formally IL-28B] and HLA type). Sixty-one of the 198 participants were HCV antibody and RNA negative, with 53 able to be examined longitudinally for HCV-specific IFN-γ ELISpot T cell responses.

RESULTS

Ten of the 53 HCV antibody and RNA negative participants had detectable HCV-specific IFN-γ responses at baseline (18%). The magnitude of IFN-γ responses averaged 131 +/- 96 SFC/106 PBMC and the breadth was mean 1 +/- 1 pool positive. The specificity of responses were mainly directed to E2, NS4b and NS5b. Participants with (10) and without (43) HCV-specific IFN-γ responses did not differ in behavioral, clinical or genetic characteristics (P > 0.05). There was a larger proportion sharing needles (with 70%, without 49%, P = 0.320) and a higher incidence of HCV (with 35.1 per 100 py, 95% CI 14.6, 84.4, without 16.0 per 100 py, 95% CI 7.2, 35.6, P = 0.212) in those with IFN-γ responses, although not statistically significant. Half the participants with baseline IFN-γ responses became HCV RNA positive (5/10), with one of these participants spontaneously clearing HCV. The spontaneous clearer had high magnitude and broad Th1 responses, favorable IFNL3 genotype and favorable HLA types.

CONCLUSIONS

This study demonstrated the detection of HCV-specific IFN-γ responses in HCV antibody and RNA negative individuals, with a tendency for HCV-specific IFN-γ responses to be associated with HCV exposure. The potential role of HCV-specific IFN-γ responses in those who remained HCV RNA negative is of value for the development of novel HCV therapeutics.

Políticas de redução de danos no Brasil

Considerando a disseminação da epidemia de HIV e o controle de sua transmissão entre usuários de drogas injetáveis (UDI), estratégias de redução de danos foram incorporadas em diversos países, incluindo o Brasil. Considerando a emergência das drogas como tema central na agenda governamental, especialmente o crack, o presente artigo registra e discute as práticas observadas em um programa de pesquisa e atenção aos UDI: o UFO. Foram considerados aspectos tais como acesso e adesão do usuário, dificuldades de financiamento, sustentabilidade e avaliação de resultados. As etapas do estudo envolveram pesquisa documental, observação sistemática e entrevistas com informantes-chave. Destacamos características do UFO que poderiam contribuir para políticas de redução de danos no cenário brasileiro. O programa estudado se apresenta como um exemplo exitoso de iniciativas de redução de danos, obtendo sucesso no acesso e adesão desse grupo, favorecendo seu acesso aos serviços de saúde e prevenção de riscos associados ao uso de drogas.

Increased hepatitis C virus vaccine clinical trial literacy following a brief intervention among people who inject drugs

INTRODUCTION AND AIMS

While people who inject drugs are at high risk of hepatitis C virus (HCV) infection and will be the target population for future HCV vaccine trials, little is known about clinical trial literacy (CTL) in this group. We assessed the impact of a brief intervention (BI) designed to improve HCV vaccine CTL among people who inject drugs in Sydney, Australia.

DESIGN AND METHODS

People who inject drugs enrolled in a community-based prospective observational study between November 2008 and September 2010 (n = 102) completed a CTL assessment followed immediately by the BI. Post-test assessment was conducted at 24 weeks.

RESULTS

The median age of the sample was 27 years, 73% were male and 60% had 10 or less years of schooling. The median time since first injection was 5 years and 20% reported daily or more frequent injecting. The mean number of correct responses increased from 5.3 to 6.3/10 (t = -4.2; 101df, P < 0.001) 24 weeks post-intervention. Statistically significant differences were observed for three knowledge items with higher proportions of participants correctly answering questions related to randomisation (P = 0.002), blinding (P = 0.005) and vaccine-induced seropositivity (P = 0.003) post-intervention.

DISCUSSION AND CONCLUSIONS

A significant increase in HCV vaccine CTL was observed, suggesting that new and relatively novel concepts can be learned and recalled in this group. These findings support the feasibility of future trials among this population. [Correction added on 21 November 2012, after first online publication: T-score for mean number of correct responses was corrected to '-4.2' in the Results section.]

Motivators and barriers influencing willingness to participate in candidate HCV vaccine trials: perspectives of people who inject drugs

BACKGROUND

A safe and efficacious vaccine may be the most efficient and cost-effective strategy for controlling the hepatitis C virus (HCV) epidemic among people who inject drugs (PWID) and several candidates are in development. However, little is known about the factors that influence willingness to participate (WTP) in candidate HCV vaccine trials among this group.

METHODS

HCV seronegative PWID recruited between 2008 and 2010 as part of a prospective observational cohort study in Sydney, Australia were asked whether they would be willing to participate in a future candidate hepatitis C vaccine trial and to provide reasons to explain their decision.

RESULTS

Of 113 participants, 74% indicated WTP, 15% were unwilling to participate and 11% reported WTP that was contingent on vaccine characteristics and trial design issues. The most commonly reported motivator for hypothetical trial participation was altruism, followed by potential health benefits, financial remuneration, and knowledge gain. Barriers to hypothetical participation included fears about possible harms to health, such as concerns about vaccine safety, side effects, and acquiring HCV from the vaccine; other barriers included mistrust of biomedical research and time constraints.

CONCLUSIONS

These results may be useful in designing strategies to enhance HCV vaccine trial recruitment and retention and have ethical implications for developing informed consent processes and standards of care.

Candidate hepatitis C vaccine trials and people who inject drugs: challenges and opportunities

People who inject drugs (PWID) are at high risk of HCV. Limited evidence of the effectiveness of prevention interventions and low uptake of treatment in this group highlight the need for increased investment in biomedical interventions, notably safe and efficacious vaccines. While several candidates are currently in development, field trials in PWID present challenges, including ethical issues associated with trial literacy, informed consent and standards of care. Significant biological and social factors and differences between HIV and HCV suggest that HCV warrants targeted vaccine preparedness research to lay the groundwork for successful implementation of future trials.